Invasive insects pose an increasing risk to global agriculture, environmental stability, and public health. Giant pine scale (GPS), Marchalina hellenica Gennadius (Hemiptera: Marchalinidae), is a phloem feeding scale insect endemic to the Eastern Mediterranean Basin, where it primarily feeds on Pinus halepensis and other Pinaceae. In 2014, GPS was detected in the southeast of Melbourne, Victoria, Australia, infesting the novel host Pinus radiata. An eradication program was unsuccessful, and with this insect now established within the state, containment and management efforts are underway to stop its spread; however, there remains a need to understand the insect’s phenology and behaviour in Australia to better inform control efforts. We documented the annual life cycle and seasonal fluctuations in activity of GPS in Australia over a 32 month period at two contrasting field sites. Onset and duration of life stages were comparable to seasons in Mediterranean conspecifics, although the results imply the timing of GPS life stage progression is broadening or accelerating. GPS density was higher in Australia compared to Mediterranean reports, possibly due to the absence of key natural predators, such as the silver fly, Neoleucopis kartliana Tanasijtshuk (Diptera, Chamaemyiidae). Insect density and honeydew production in the Australian GPS population studied varied among locations and between generations. Although insect activity was well explained by climate, conditions recorded inside infested bark fissures often provided the weakest explanation of GPS activity. Our findings suggest that GPS activity is strongly influenced by climate, and this may in part be related to changes in host quality. An improved understanding of how our changing climate is influencing the phenology of phloem feeding insects such as GPS will help with predictions as to where these insects are likely to flourish and assist with management programs for pest species.

The xylem feeder Bathyllus albicinctus (Aphrophoridae: Cercopoidea: Hemiptera) has been identified as one of the most abundant and widely distributed cercopoid insects in Australia. This native Australian species might potentially vector Xylella fastidiosa, an exotic and deadly plant pathogen, if it were to arrive in Australia. Previous surveys indicated that B. albicinctus is associated with a wide range of plants, further elevating its impact as a potential disease vector. However, it is unknown if all the associated plants are equally viable hosts. Due to the variety of plant records and distribution across the southern half of Australia, it was expected that B. albicinctus would successfully feed and survive on a taxonomically diverse range of plants. In the present study, a small-scale no-choice feeding-controlled glasshouse experiment was completed where insect nymphs were supplied with plants that are economically significant and susceptible to X. fastidiosa. In this experiment, we monitored the maturation and longevity of B. albicinctus, specifically by comparing insect cohorts distinguished by nymph size, host species, or feeding season. This study documented important interactions of life-history factors for B. albicinctus, including suitability of host plant species among insect sex and season. This could indicate that the ability for B. albicinctus to spread X. fastidiosa may vary with host plant species and time of year. These findings provide a vital knowledge framework for future research and surveys to consider when implementing control efforts or tracking plant pathogens that may be spread by B. albicinctus.